1. Field of the Invention
The present invention relates to a mark printing/verifying device which prints a mark such as a barcode, then scans and reads the mark, and verifies the printing result, and a mark printing/verifying method and a mark printing control method thereof.
2. Description of the Related Art
Recently, automatic recognition systems using marks such as barcodes are widely used in various fields. The barcode, in which information is encoded and indicated in an array of spaces and bars, is printed directly on an item or printed on a sheet such as a tag or label attached to an item. The information included in the printed barcode is read using a dedicated optical information reading device (a barcode reader).
On the other hand, in a mark printing device (a barcode printer), a barcode is transferred to a sheet by selectively allowing a thermal head to generate heat based on image data of a barcode to be printed, bringing a thermal transfer ribbon and a sheet overlaid one upon the other into pressure contact therewith, and melting ink contained in the thermal transfer ribbon.
In this event, the optical information reading device cannot correctly read barcodes that are not normally printed by the mark printing device, for example, a barcode having a partial lack caused by a crease in the thermal transfer ribbon or contamination on the thermal head, a barcode having a bar size out of a specified range because of excess or deficiency of heat of the thermal head, and the like. Then, the barcodes having printing defects mixed in normally printed barcodes cause a delay in read work.
Hence, mark printing/verifying devices have been conventionally developed which print barcodes, then scan and read the barcodes by scanners, and verify the printing results (whether the barcodes are normally printed).
For example, as found in JP5-4912B, there is a self correcting-type printing/verifying device which prints a mark such as a barcode on a sheet by a print head such as a thermal head, then scans and reads the mark by a scanner, calculates deviation between dimensions of some portions of the read mark with specified dimensions corresponding thereto, and changes printing drive signals to be applied to the thermal head in a manner to decrease the deviation, thereby adjusting the physical dimensions of the mark. Note that, to prevent a decrease in printing speed, the scanner is driven reciprocating in the lateral direction of the sheet and scans the mark while paper is being conveyed in this device.
Further, as found, for example, in JP8-25321B, there is another mark printing/verifying device which is configured to print a mark on paper, then shift the scanner in a direction of a paper conveying direction during mark scan during which the scanner scans and reads the mark in a direction perpendicular to the paper conveying direction while the paper is being conveyed, so as to be able to scan even a mark having a small length in the paper conveying direction without a decrease in printing/verifying speed (hereafter called “throughput”).
However, the conventional mark printing/verifying devices described in the aforementioned two patent documents, in which the scanners scan marks while paper is being conveyed, have problems that they are suitable to scan and verify barcodes (linear codes) made by encoding information in one dimension, but cannot verify two-dimensional codes having a high density of information and an extremely small symbol size (minimally several millimeters square).
It should be noted that the two-dimensional code is a symbol created by encoding information in two dimensions, which has been developed to solve many problems associated with barcodes such as its small amount of information, low density of information, large symbol, incapability of using kana and kanji (Japanese letters and Chinese letters), impossibility to read when it becomes dirt, limited in read direction, and so on, and spread rapidly in recent years to be coexistent with barcodes.
Further, the two-dimensional codes include a stack-type two-dimensional code (also referred to as a two-dimensional barcode) such as PDF417 in a form in which barcodes are stacked and a matrix-type two-dimensional code such as Data Matrix in a form in which black cells in squares of a “go board” (grid), either of which has a low stack height and a small cell size and, as a result, the aforementioned conventional mark printing/verifying devices fail verification and compensation printing based on its result.
Hence, there is a conceivable method of first reading all the image of two-dimensional code using a CCD or laser for mark scan, storing the whole image data once in a memory, then comparing dot information of a printed mark with dot information of a correct mark for verification, and decoding or compensating it.
This case, however, has a problem that a large capacity of memory is required to store the whole read image data, leading to increased cost.
There is an additional problem that it takes time to read and verify the data, resulting in a lowered throughput.